Basically, many users feel that Apple should have let them know that a software update was going to slow down their phone, or given them a choice not to turn the update on. Apple says a phone with the feature active can take longer to launch apps and can display lower frame rates.

Here’s how Apple’s CEO explained the problem in an ABC interview earlier this week:

“About a year ago, we released some code, that essentially what it does, is all batteries age over time, and they become unhealthy in a point in time,” Apple CEO Tim Cook said in his first public comments on the controversy. “An unhealthy battery has a probability that it will create an unexpected restart.”

“When we did put it out, we did say what it was, but I don’t think a lot of people were paying attention, and maybe we should have been clearer as well,” he continued.

But even an Apple user who was paying attention would not have known about the feature had they downloaded the update shortly after it was available. Apple documents any major new features or improvements alongside new software updates in messages called “release notes.” For people who don’t read tech blogs, this is often the way they learn what’s new in a software update.

There was no mention of the CPU throttling feature or “power management” included with the release notes that accompanied the software update on January 23.

However, release notes associated with the software update, quietly revised on Apple’s website after the software’s release, now mention “power management during peak workloads.”

For minor updates, release notes can be as short as a sentence, but for major updates, like when a new iPhone comes out, they can be pages long.

On January 23, the update was called a “point update,” signaling that Apple did not consider it a major software update.

The release notes only said it contained “bug fixes,” and security patches, according to Forbes, which published a screenshot of the release notes from an iPhone, which is different from the notes now listed on Apple’s website.

Blog posts from 9to5Mac and MacRumors at the time also say that the release notes were short and didn’t mention power management.

Apple finally acknowledged the battery feature one month later after iOS 10.2.1 on February 23, in a press statement reported by TechCrunch, saying the feature was already on “over 50% of active iOS devices” and that its test data showed that it had reduced the occurrence of an annoying shutdown problem.

TechCrunch also published some high-level explanation of the bug on February 23 and why Apple addressed it. That was the first time Apple publicly disclosed the feature that is now drawing attention from Congress, and over half of iOS device users had already installed it with no warning or signal of any new power management feature.

It also improves power management during peak workloads to avoid unexpected shutdowns on iPhone.

Revising release notes weeks after they were first published is unusual. But Apple had been avoiding questions about the shutdown issue for over six months.

In December, Apple said that it “extended” the CPU-throttling feature to the iPhone 7, which is a newer model of device than the iPhones that were experiencing the shutdown issue that Cook was talking about. However, the release notes for that update did not mention a power management feature, either.

‘Maybe we should have been clearer’

Whether Apple should have more clearly communicated the changes has now attracted the attention and ire of US Congress, lawyers, and consumers, who all want more information from Apple on how it handles iPhone processor speeds.

“There should have been other things that Apple did to make clear to the public that the CPU performance was going to be throttled and they just didn’t do that,” said Scott Cole, an Oakland attorney who recently filed a complaint on behalf of aggrieved parties about the Apple battery slowdown.

“Prior to installation of an iOS software update, does Apple inform users of the potential for a reduction in processor performance associated with an update?” asks a letter from the House Committee on Energy and Commerce sent to Cook earlier this month.

Apple is also facing a slew of class-action lawsuit complaints, as many as 45, in various courts around the country, according to Cole.

“Our responsibility is to our own client and what’s referred to as the ‘putative class,’ or all the people who purchased various iterations of the iPhone 6 and 7, that frankly were duped along the way in a couple of ways,” Cole said. “First we intend to prove in the cases that Apple should have used a larger battery to begin with.”

“But more importantly, Apple kept information from consumers for quite some time, didn’t reveal the fact that the rollout of a new operating system was going to have the effect of dropping back phones,” he continued, declining to comment on the specific timing or content of Apple’s iOS release notes.

Apple didn’t respond to multiple requests for comment. But answers to these questions will eventually emerge. The House letter to Apple requests a response by next Friday. And several international oversight agencies have opened their own investigations.

Cole also expects the class-action lawsuits to progress over the next year. The first step, likely happening over the next few months, could be a process called “multi-district litigation,” where the defendant – in this case Apple – doesn’t want to fight a number of different cases in different courts, so it petitions to have the suits combined into one case.

After that, the case could be settled in a matter of months, or a matter of years, depending on what the lawyers find. “These cases, they generally have a life of a couple of years,” Cole said.